The present invention generally relates to semiconductor devices and methods of producing the same, and more particularly to a semiconductor device having a radiation part for radiating heat and a method of producing such a semiconductor device.
There are semiconductor elements which generate heat during operation, and it is necessary to efficiently cool such semiconductor elements. Conventionally, there is a semiconductor device having radiation fins for cooling the semiconductor element provided on a package which encapsulates the semiconductor element. From the functional point of view, it is desirable that the radiation fins have a high radiation characteristic. On the other hand, from the production point of view, it is desirable that the radiation fins can be produced at a low cost.
FIGS. 1 and 2 show an example of the conventional semiconductor device. A semiconductor device 1 generally includes a package 2 and radiation fins 3. The package 2 is made of a resin, while the radiation fins 3 are made of a metal such as aluminum.
The package 2 encapsulates a semiconductor element (not shown) by a resin molding, and the semiconductor element is protected by this package 2. A plurality of lead frames 4 are provided as shown. The lead frames 4 connect to the semiconductor element within the package 2, and also project from the package 2 so that the lead frames 4 may be connected to a circuit substrate or the like.
In order to improve the radiation efficiency of the radiation fins 3, the radiation fins 3 are shaped so that the surface area thereof is increased. Conventionally, an adhesive agent having a satisfactory thermal conductivity is used to mount the radiation fins 3 on the package 2.
However, according to the conventional semiconductor device 1, the package 2 is made of the resin while the radiation fins 3 are made of the metal. For this reason, the package 2 and the radiation fins 3 must be produced by independent processes, and there is a problem in that the production process of the semiconductor device 1 becomes complex. In addition, the radiation fins 3 have a complicated shape so as to improve the radiation efficiency. As a result, there are problems in that it is troublesome and difficult to form the complicated shape of the radiation fins 3 from the metal, the process of forming the radiation fins 3 is unsuited for mass production, and the cost of the radiation fins 3 and thus the cost of the semiconductor device 1 becomes high.
On the other hand, because the radiation fins 3 are bonded onto the package 2 using the adhesive agent, the strength and heat resistance at the bonded part are poor. Furthermore, the radiation characteristic at the bonded part is inconsistent because of voids generated at the bonding surface and/or within the adhesive agent. For these reasons, there is a problem in that the reliability of the semiconductor device 1 becomes poor. Moreover, there is also a problem in that it is difficult to control the positioning accuracy of the radiation fins 3 with respect to the package 2 and the height of the radiation fins 3 when the adhesive agent is used to mount the radiation fins 3 on the package 2.